Robert S. Mueller III, the former FBI director who transformed the bureau into a terrorism-fighting force after the Sept. 11, 2001 attacks and later served as special counsel investigating ties between Russia and Donald Trump's presidential campaign, died Friday night. He was 81.

"With deep sadness, we are sharing the news that Bob passed away" on Friday night, his family said in a statement Saturday, asking that their privacy be respected. Trump posted on social media about Mueller's death, writing "Robert Mueller just died. Good, I'm glad he's dead" and adding "He can no longer hurt innocent people!"

Mueller served as FBI director for 12 years, beginning just one week before the Sept. 11 attacks. The attacks immediately shifted the bureau's priority from solving domestic crime to preventing terrorism. Under Mueller's leadership, the FBI moved 2,000 of its 5,000 criminal program agents to national security work, fundamentally transforming the agency's mission and operations.

After leaving the FBI in 2013, Mueller returned to public service in 2017 as special counsel investigating whether the Trump campaign coordinated with Russia during the 2016 presidential election. His team brought criminal charges against six of Trump's associates, including his campaign chairman and first national security adviser. Mueller's 448-page report, released in April 2019, identified substantial contacts between the Trump campaign and Russia but did not allege a criminal conspiracy.

The report detailed Trump's efforts to control and potentially shut down the investigation, though Mueller declined to determine whether Trump had broken the law, citing Justice Department policy against indicting a sitting president. Mueller wrote that his team could not conclude "that the president clearly did not commit obstruction of justice."

Mueller was born in New York City and served as a Marine officer during the Vietnam War, earning a Bronze Star and Purple Heart. After earning a law degree from the University of Virginia, he became a federal prosecutor, rising through U.S. attorneys' offices and eventually overseeing high-profile prosecutions including cases against Panamanian dictator Manuel Noriega and crime boss John Gotti before his appointment as FBI director by President George W. Bush.